0,1

Thanks to Dean Hickerson (dean(AT)math.ucdavis.edu) for a very efficient program.

Needs[ NumberTheory`NumberTheoryFunctions`]; pm1[{k_}] := {1, k - 1}; pm1[lst_] := Module[{a, m, v}, a = lst[[1]]; m = Times @@ Rest[lst]; v = pm1[ Rest[lst]]; Union[ ChineseRemainder[{1, #}, {a, m}] & /@ v, ChineseRemainder[{-1, #}, {a, m}] & /@ v]]; nexttri[1] = 3; nexttri[n_] := Module[{s}, s = (pm1[Power @@ # & /@ FactorInteger[4n]]^2 - 1)/8; For[i = 1, True, i++, If[s[[i]] > n, Return[ s[[i]]] ]]]; a[0] = 15; a[n_] := a[n] = nexttri[ a[n - 1]]; Table[ a[n], {n, 0, 8}]

Cf. A068776, A068142.

Adjacent sequences: A068510 A068511 A068512 this_sequence A068514 A068515 A068516

Sequence in context: A039450 A127069 A095129 this_sequence A033480 A041434 A136430

nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Mar 19 2002